Nitrous duty% vs. flow relationship ?

[sportbikeryder]

I think way too much is being put into the mechanics of nitrous rather than making power.  Spraybars work just fine with pulsed controllers. Adding fuel via a wet jet or through an increased pulsewidth in the FI works just fine as well. Running your bottle pressure at 1000, 1100, 900, or 800 psi works just fine as well.

If the goal is to make the absolute most amount of power for a given jet size, then the additional thoughts may be needed.

As far as I know, there are no classes in any motorycle racing that limit the size of the nitrous jet. If you want more power, increase the jet size.

Many people argue this, but until you are up over 125-150 hp, it has always worked.

It really makes no difference wether a "65 shot" makes 59, 65, or 77 horsepower. Whatever it makes, replacing it with an "80 shot" will make more and will need a bit more fuel.

Our last dyno'd bike made only a three hp difference from 11.7 - 13.4 :1 AFR.  This also shows that moving up or down a jet size would still be in a power making range of AFR.

Just seems like it woudl be easier to say "pulse the solenoid, add fuel, and remove timing..."  I doubt a great deal (zero) of additional performance will result from removing spraybars and the like.

[Gasabusa1]

Its a fair point,all nitrous works in a fashion,although I'd never run a nitrous kit out at a 13.4 A/F.  We normally see a bigger gain than 3bhp for the variance of A/F you talk about there its normally in the 10's of bhp.
We're kinda done with the nitrous on your equivalent of Pro Streetbike thing over here. We've probably run as many types of system configurations as you can think up.The best our bikes ran was 7.8 at 184mph with a base horsepower of 190-200bhp ish.Our guys want a cheap motor and to make up the rest on nitrous so we end up trying to stick 200bhp plus in the motors.When you get to this end the whole nitrous deal is finely balanced.Its clearly a better idea to go with a big capacity full house motor and less nitrous like the HTP setup but the motor alone is £6000 over here and that is the cost of a turbo kit and a fair way down the road to a motec system.
In the end all our nitrous guys in this class have either folded and gone turbo or changed class.

The main concern I have with the dry system software you are proposing is in the fueling. If you compare it to a wet pulsing system you're not suppling the fuel in the same manor.In a wet pulsed system you switch the pair of soliniods on together and the mixture is the same when flowing ie the jet sizes are the same so arguably the mixture is the same for the pulsed section as it is for the 100% on section.As soon as you move to dry you seem to want to effectively change the fuel jet size down by reducing the fuel when the nitrous is pulsed on.
When a 20% pulsed dry system is working the power is still full but for a shorter time,thats to say in 10 cycles of the engine the nitrous is on for 2 cylces.For those 2 cycles it needs the same burst of fuel to match the nitrous NOT 20% for all the time the nitrous is pulsed on and off.By doing this you will be effectively running the bike lean when the nitrous is pulsed on and slightly rich when its not.

[PetriK]

Is there any research data on this - as my personal assesment is very different and outlines the superiority of dry systems compared to wet systems based on the below:

1) Liquids do not compress, hence travel about the same speed from opening the injector (or solenoid) to the cyclinder
2) Gases compress, hence pulsating the nitrous solenoid does not completely cut and reopen the gas flow, rather just reduces the gas flow
3) Wet systems do not synchronize the injector pulses with valve opening

All this means to me the following:
a) Fuelpulses in wet systems do not synchronize with the valve opening, hence causing the fuelcharge being inconsistent between cylinder fills. Fuel droplets hitting the valves will vaporize and cause the fuel travel further away from valve. Therefore there will be big fuellind differences in wet systems.
b) Nitrous pulsation generates some pulses into the flow, but does not either cut the flow completely due to the gase compressibility. As gas is compressible and there is some flow resistance in the flowing system, therefore the cylinder fill of nitrous charge is always about the same.
c) Dry systems will provide optimum fuel charge for each cyclinder fill as the injectors operate to charge the cylinder with optimum fuel charge

I am a person who believes on documented research data so all ears now to hear views and comments... ?

[Gasabusa1]

I'm also a big fan of documented evidence Petrik unfortunately you won't will find any 'real' data to answer your points above.I think Trevor Langfield will be the best guy to ask on the technicalities above but most answers will be 'theory' backed up with few measured results.My initial response would be that the nitrous solinoid is dealing with nitrous in a liquid state that changes into a gas when the soli opens.The fuel injection duration for an aspirated Busa is somewhere around 80% duration when measured by oscilloscope and is therefore spraying onto a closed inlet valve for quite a while.The early Busa is sequential upto a point but is effectively a group injection system at high rpm as the squential offset has little effect as the valve is shut whilst the fuel is being sprayed.
I'm a big fan of dry systems and especially ECU programmable units, I've worked with these dry systems using Motec for over 5 years.The controllability is great and gives you many options when configuring the way to add the nitrous.The guy who ran at Bonneville was on a dry system using Motec.
I finally drew the conclusion that the only real way of measuring scientifically the true effect of nitrous and its distribution was to have in cylinder pressure sensors.The UK Ford development centre has these for engine development,they measure a spread on petrol burning engines of upto 20% BETWEEN STROKES thats not cylinders but the same cylinder with a succession of firing strokes.So you can imagine what a shot of nitrous is doing in there and what the possible spread is.
Even if you had a soliniod that was fast enough to open in sync with the inlet valve the jet size prorata would be huge especially when trying to maintain in sync power at high rpm.
Trevs Revo(like turning on a tap) is probably the real answer but how far that is up the development trail is unknown,I think the HTP guys have run it though.

[PetriK]

Bought the book - shall be in touch with him when have had to read first of his thinking...

Do you mean that this way of thinking comes from him ?

[Gasabusa1]

Bought the book - shall be in touch with him when have had to read first of his thinking...

Do you mean that this way of thinking comes from him ?

Trevs as nutty a bag full of spanners but he knows his stuff.

I think you have to take the commercial point of view into account the only people interested in making more than double or close to triple the base horsepower in a motor are largely motorcycle based.To do this you will need to develop the kits past whats currently available now,with except of the Revo theres not been much of a change in nitrous hardware technology in the past 20 or 30 years.The motorcycle nitrous business is probably 10% of nitrous sales.
Nearly 10 years ago I started spraying using dry systems on Busa's,the questions you ask above are very simialr to the ones I was asking back then so far the only answers I really have are theories.The in cylinder pressure measurements are the ones that will answer the bulk of the questions BUT they are £10K each over here.!!!

[PetriK]

We too have been trying to get kits for measuring in cylinder pressures, prices are still ok - but the replacement parts, maintanability and our special requirement lenght spark plugs (for very tight head to piston) have made this impossible excersise.

Read the book from "Wizard of Nos". If I put aside that its slightly outdated particularly from dry systems part and contants some marketing aspects , there is some quite interesting points though to mention some:
- The velocity of nitrous due to the pressure is very high compared to gasoline in the lines
- The wet system solenoid (pulsoid) opening rate that works against the pressure means that the solenoids must be matched for purpose
- Showerhead obviously is the distribution block recommended
- ...

Been also thinking about this alledged problem of pulsating nitrous not hitting the cylinders equally with fuel and would like to come up with a some themes for discussion:
- In my head the air/n20 mixture travels at velocity of 300-400fps under full power. Additionally the air/n20 mixture is spitted backwards at enginerpm/2 due to the closing and opening of the intake valve as per the illustration below.

All this means that as long as the nitrous is shot to the airstream above the injectors the pulsation of any nitrous as it happens upstream of the showerhead is reduced rather to a constant flow of the gas that gets a fairly good mixing due to the turbulence of the TPS plates...

[Gasabusa1]

I was first alerted to how the pulsing effected the engine when standing outside the dyno room whilst my buddy tested a single shot 220bhp of nitrous on 180bhp motor.The exhaust note could clearly be heard pulsing as the nitrous hit and got less as the progressive hit harder etc.This was with the nitrous injected into the bellmouths.We eventually went to 2 stages pulsed to remove the big pulse hits on the motor.That version was far more reliable than the single big hitter and the pulsing exhaust note far harder to determine.
I think you maybe correct with the nitrous being injected into the airbox smoothing out the hits to a certain extent but as I mentioned to you before the high 10000rpm power seemed to suffer on our setup,but give it a go it was only a few bikes we ran.
The ultimate way would be a pure nitrous motor with a positive pressurised airbox......but then you have a turbo anyway

[PetriK]

Was that pulsation on a wet system where the gas and fuel travels different speeds causing problems to run the engine. Gas flow is more steady and fuel flow goes more up and down...

I will do some desktop testing of this when I have time with a nitrous system on the desktop just to check this.

EDIT - just realized that I can generate a programmable feature that sets Fuelpulse increase: increase fuelpulse only when nitrous duty cycle is active / increase fuelpulse when nitrous windows active.

In practise this means that the user can choose if the additional fuel is delivered all the time or only when nitrous duty cycle is active and we can put an end to the discussion of nitrous pulsation with dry systems.

http://www.freepatentsonline.com/5269275.pdf

[PetriK]

So now the latest not yet released desktop test version of ecueditor 2.1 (http://www.ecueditor.com) has a button which makes the ecu to emulate the wet kit fuelling. Ie. there is option to turn the additional fuel on only when the nitrous duty cycle is on (Wetkit type fuel pulsing, emulation on) and if someone wants to have constantly higher fuel delivery then the additional fuelling can be always on (Wetkit type fuel pulsing, emulation off).

In practise this means that when the Wetkit type fuel pulsing emulation is on, the additional fuel pulses are synchronized with nitrous solenoid pulses - if emulation is off then the additional fuelling is on all the time.



ps. The ramp up time and fuel delay time are features that are waiting to be implemented after the initial testing of core functionality.

[Gasabusa1]

Was that pulsation on a wet system where the gas and fuel travels different speeds causing problems to run the engine. Gas flow is more steady and fuel flow goes more up and down...

I will do some desktop testing of this when I have time with a nitrous system on the desktop just to check this.

EDIT - just realized that I can generate a programmable feature that sets Fuelpulse increase: increase fuelpulse only when nitrous duty cycle is active / increase fuelpulse when nitrous windows active.

In practise this means that the user can choose if the additional fuel is delivered all the time or only when nitrous duty cycle is active and we can put an end to the discussion of nitrous pulsation with dry systems.

http://www.freepatentsonline.com/5269275.pdf

I really only ever worked on/developed dry systems, the audiable pulsing was on a dry system......either I'm missunderstanding you or vice versa,but if you pulse a nitrous soliniod there is no real way you can overcome the rise and fall in nitrous power with the rise and fall in nitrous density.The further away from the valve and the smaller the power increase I guess the better, but with big stuff I've found it impossible,like I say nitrous is full of theories and tends to fall short practical results.All I can tell you is that when you stand next to a bike thats getting a 200bhp dry hit you CAN  hear the gas pulses hitting,especially at 20%.
I guess that if you have a large airbox and feed in at the entry that kinda like a resistor capacitor effect you should be able to 'smooth the pulses' to a degree,like I said I've run up enough big horsepower nitrous bikes to know that when you get so far its best to change to turbo.Its a shame because the controller you have there and the ones you can configure in Motec are superb and far easier to set correctly than boost controllers, and the power hits where you tell it and doesn't have to rely on the turbo to spool to where you want it to be IMPO.

Still give it a go I could well be wrong it'd be great to see a readily available 200bhp plus nitrous kit thats reliable.

[PetriK]

We are on common ground here, very much.  This is also a very good conversation as it at least my brains to think how to overcome the pulsation issue. This pulsation I do see this as an issue for both dry and wetkits as power increase comes at each 10hz or what ever timer the controller is not set on. If duty is 20% then 2 tenths of a second there is 40% more power (depending on solenoid etc.). No doubt that this is audible. Now what we can do with dry kits like this is to be able to match the fuel to nitrous delivery pulsation, way better than with wet kits as with wet kits the fuel speed vs nitrous speed, i.e. line lenghts become an issue due to the different speeds the fuel and nitrous travel. No wonder why NX systems and WON have put so much effort into the nozzle design. I recall NX even patenting their nozzle.

With mixing the nitrous to intake air properly is so cruicial for proper rampup, as what happens in that particularly at lower RPM:s the total air volume in is lower.

Anyhow as I have never tuned a motorcycle with more than 80hp nitrous (and there only has been once a 150hp nitrous bike in the shop for dynoing) I would be very interested to know which kind of engines are we referring here to ? Particularly the RPM range and displacement is interesting. Please see the below table for reference why.

[sportbikeryder]

Is there any way to determine if the fuel adn nirtous pulses are in sync? Not sure how you would ever know if they were in phase or not.

also, I doubt that this would prevent any noticable difference in the aforementioned exhaust note pulsing (I personally have never noticed this) as the power pulses would still be there if you pulse the fuel as well as the nitrous. just woudln't be rich / lean / rich / lean (if the fuel and nitrous was times correctly).

[PetriK]

Is there any way to determine if the fuel adn nirtous pulses are in sync? Not sure how you would ever know if they were in phase or not.

To me the fuel and nitrous are always out of sync as fuel travels different speed than nitrous. With dry system we can at least aim to have most fuelling done synchronized with valve opening. With wet kit we shoot the fuel and nitrous same time, but due to the different speeds (line pressure 750psi vs 43psi) the fuel arrives later than nitrous to the intake (exact time delay depending on solenoid distance to jet). With latest version of ee2.1 you can choose which method of fuelling you prefer.

What is discussed above (how I interpreted this), is that in both wet and dry systems with controllers the nitrous flow may be pulsated depending on system design and power levels. Thats because the solenoid duty is 10Hz (10 nitrous pulses/s) where as engine maybe running 10000rpm (5000 ignition pulses/s). This means that at 20% duty cycle (without solenoid and line delays) the nitrous will be on for 1000 ignition pulses and off for 4000 ignition pulses.

[Gixx1525R]

That is an issue that I figured out 10 years ago. I made a Hybrid Wet/Dry system that I have been using with great results. I have sprayed as much as a 200 shot Dry. The Nitrous and the Fuel both hit the intake tract at .300 to .450 of a second. If you want pics just let me know

[Gixx1525R]

 This was before the days of Billet Fuel rails,Bigger Injectors and switchable maps. The Fuel pressure regulator on the left is for the main fuel system. The one on the right is for the Nitrous.  When the Nitrous system is  activated it turns on the Nitrous fuel pump,once the WOT switch is actvated both Solenoids are open. Since the main fuel system and the Nitrous fuel system feed into the Fuel rail there is very little delay in the fuel delivery. The fuel is back filled to outlet side of the fuel solenoid from the fuel rail. When the Nitrous pump is running the fuel is filled to the inlet side of the solenoid. Once activated the fuel pressure bumps up by 10 psi through the injectors to 55psi (I have the main fuel system set at 45psi). This more of a blending of Wet/Dry since 2 fuel pumps are used but the Nitrous is added inside the Airbox. It may sound complex but it is actually pretty simple. On my 1363cc Busa (at that time) it made 200RWHP and I sprayed a 200 shot Dry.

[PetriK]

so increasing the frequency for lower duty cycles is the key ?

[Gasabusa1]

Forgive cos I is stupid,am I right in assuming you have 2 fuel systems inc 2 pumps and 2 regs feeding 1 fuel rail?I see something like this before only the guy simply uprated the pump and reg and put a regulated air supply on the back of the regulator to raise/increase the fueling.
Thats an amazing increase in power on stock injectors the best we managed at 75psi on stock injectors was around 300bhp,I guess we were doing something wrong
What sort of qtrs,terminals or top speeds did you run on this setup?

[Gixx1525R]

Forgive cos I is stupid,am I right in assuming you have 2 fuel systems inc 2 pumps and 2 regs feeding 1 fuel rail?I see something like this before only the guy simply uprated the pump and reg and put a regulated air supply on the back of the regulator to raise/increase the fueling.
Thats an amazing increase in power on stock injectors the best we managed at 75psi on stock injectors was around 300bhp,I guess we were doing something wrong
What sort of qtrs,terminals or top speeds did you run on this setup?

What Fuel pumps did you use? Yes I use 2 fuel  pumps

[Gasabusa1]

Bosche 044

[Gixx1525R]

The Bosch 044 inline fuel pump provides 80 GPH of flow and operate at an amazing 72.5PSI. It is possible that you surpassed the capability of the stock injectors.
.
I use 2 T-Rex Fuel Pumps rated 50 GPH@70 PSI each

Also the stock petcock will limit the amount of fuel that the fuel pump can deliver. I run a Pingle Guzzler dual outlet petcock so there is no restriction.

[Gasabusa1]

I used the guzzlers too,the fuel system setup worked fine after on my 550bhp turbo setup albeit with bigger injectors

[PetriK]

What do you think of this way of calculating the target AFR based on nitrous shot - to me this makes sense based on what have seen on a dyno.

http://www.modularfords.com/forums/showthread.php?t=150757